: Hypothetical syllogisms (conditional arguments) can have : two valid and two invalid structures. The two valid : structures are affirming the antecedent (modus ponens) and : denying the consequent (modus tollens). The two invalid : structures, or fallacies, are denying the antecedent and : affirming the consequent. Determine if the arguments below : are valid or invalid and what form they take. The first one : has been done for you.: (NOTE: The term "modus pollens" has been used in some texts : as a version of "modus ponens." For the purposes of this : exercise, "modus ponens" will be used.): : SAMPLE: Chris and Nick would be very happy if the Browns : beat the Steelers. The Browns did beat the Steelers, so : Chris and Nick are very happy, indeed.: : Valid Modus Ponens (Affirming the Antecedent): : : 11. Madeline must have known the material for the test, : because if a person knows the material, that person will : always get an A, and Madeline was one of the students that : got an A.: : : : 12. Anastasia believes that if she treats people honestly : and with an open mind, she will have diverse friendships. : She is honest and open-minded and has friends all over the : world.: : : : 13. Roberto thought that if he worked very hard, his boss : would give him a raise or a promotion. He made sure she : noticed him, but she did not give him a raise or promotion. : He thought he must not have worked hard enough.: : : : 14. "I'm still eating too much ice cream," lamented : George. "My waist measurement is the same as it was six : months ago. I know if I didn't eat so much ice cream, I : would reduce my waist size.": : : : 15. The good way to make sure we pay fewer taxes is to : elect conservatives. We must not have elected enough : conservatives, because we are paying more taxes.: : : : 16. If my neighbor were a decent human being, he wouldn't : let his tree leaves fall onto my property. But he's not a : decent human being, so we get to clean his tree leaves as : well as ours.: : : : 17. We'll have fun and learn a lot in this course, if we : have great facilitator. We do have a great facilitator; : therefore we are learning a lot and having fun doing it!: : : : 18. If I could only understand the concept of : hypothetical syllogisms, I would get an A in class. Hurray! : I got an A in class, so I must have understood the concept : of hypothetical syllogisms.